Import envbuilder

[hanabel1]

Changes

=======

• Add newEnvbuildCmd to cmd/envbuild.go with two subcommands: env and build
  • Add circleci envbuild env subcommand that detects the tech stack of a repository and prints a JSON environment spec to stdout
  • Add circleci envbuild build subcommand that reads a JSON environment spec from stdin, writes Dockerfile.test, and runs docker build
  • Register envbuild command in cmd/root.go
  • Add github.com/CircleCI-Public/chunk-cli as a dependency (with local replace directive) to expose the envbuilder package

There are a lot of lint issues but it works.

Here are some helpful tips you can follow when submitting a pull request:

1. Fork the repository and create your branch from main.
2. Run make build in the repository root.
3. If you've fixed a bug or added code that should be tested, add tests!
4. Ensure the test suite passes (make test).
5. The --debug flag is often helpful for debugging HTTP client requests and responses.
6. Format your code with gofmt.
7. Make sure your code lints (make lint). Note: This requires Docker to run inside a local job.